Hydrolytic enzymes and

In yeasts and other fungi, the vacuole is an important organelle sharing some properties with the mammalian lysosome (an acidic compartment containing a variety of hydrolytic enzymes) and with the plant cell vacuole (responsible for metabolite storage and for cytosolic ion and pH homeostasis) [18,19]. 

Conditional stability constants have been determined for cadmium binding to humic acid in freshwater, log Kk 6.5 [27], which may be comparable to binding to humic acid coated particles. The experiments demonstrated the importance of cadmium uptake from particles rather than from the dissolved phase. The authors recognised that the overall conclusion was similar to previous studies [28], but there remain inconsistencies in the uptake levels which may be related to the heterogeneity of the systems. Uptake from the intestine into the mucosal cells was not investigated. It was presumed that the material was digested extracellularly by hydrolytic enzymes and the released metal was taken up by facilitated diffusion. 

Another possible mechanism for the racemization of amino acid esters involves the in situ, transient, formation of Schiff s bases by reaction of the amine group of an amino acid ester with an aldehyde. Using this approach, DKR of the methyl esters of proline 5 and pipecolic acid 6 was achieved using lipase A from C. ant-arclica as the enantioselective hydrolytic enzyme and acetaldehyde as the racemiz-ing agent (Scheme 2.4). Interestingly, the acetaldehyde was released in situ from vinyl butanoate, which acted as the acyl donor, in the presence of triethylamine. The use of other reaction additives was also investigated. Yields of up to 97% and up to 97% e.e. were obtained [6]. 

Peptidases such as trypsin are also hydrolytic enzymes and are important considerations for the new generation of peptide and protein drugs (see below). 

Ingested polysaccharides and disaccharides are converted to monosaccharides by intestinal hydrolytic enzymes, and the monosaccharides then enter intestinal cells and are transported to the liver or other tissues. 

Although inversion was not observed with the E. colt alkaline phosphatase, it has been observed for ribonucleases and many other hydrolytic enzymes and for most kinases transferring phospho groups from ATP. The difference lies in the existence of a phospho-enzyme intermediate in the action of alkaline phosphatase (see Eq. 12-38). Each of the two phosphotransferase steps in the phosphatase action apparently occurs with inversion. The simplest interpretation of all the experimental results is that phosphotransferases usually act by in-line -like mechanisms which may involve metaphosphate-ion-like transition states that are constrained to react with an incoming nucleophile to give inversion. An adjacent attack with pseudorotation would probably retain the original configuration and is therefore excluded. 

Biocatalysts, mainly hydrolytic enzymes and oxidoreductases, have been used for organic reactions due to their excellent enantioselectivities and environmentally friendliness.1 Typical enzymatic reactions used for the organic synthesis are shown in Figure 1. Especially, hydrolytic enzymes for kinetic resolutions of racemates have been utilized widely because of their high stabilities, wide substrate specificities, lack of cofactor requirements and high availabilities. 

Optical resolution of racemic compounds by biocatalysts has been a useful method as shown in this review. For this purpose, two types of biocatalysts are mainly used hydrolytic enzymes and oxidoreductases. 

Alternatively, the calcium stores may be concentrated by lamellar bodies from the intercellular fluids released during terminal differentiation. The lamellar bodies are thought to be modified lysosomes containing hydrolytic enzymes, and a potential source of the hyaluronidase activity. The lamellar bodies fuse with the plasma membranes of the terminally differentiating keratinocytes, increasing the plasma membrane surface area. Lamellar bodies are also associated with proton pumps that enhance acidity. The lamellar bodies also acidify, and their polar lipids become partially converted to neutral lipids, thereby participating in skin barrier function. 

In addition to the variation among feedstocks, the requirements for fermenting microbes can differ with different pretreatment and fermentation processes. Currently, the most attractive process for biomass to biofuel conversion is simultaneous saccharification and fermentation (SSF), in which the hydrolytic enzymes and fermenting microbe(s) are mixed together and work under the same environment (Punnapayak and Emert, 1986). Use of SSF can mini-... 

The region between the outer surface of the cytoplasmic membrane and the inner surface of the outer membrane is called the periplasm. This occupies a distance of about 12-15 nm, is gel-like in consistency and, in addition to the peptidoglycan, contains sugars and an abundance of proteins including hydrolytic enzymes and transport proteins. Table 3.2 summarizes the major differences in wall composition between Gram-positive and Gram-negative cells. 

N-formylmethionyl peptide receptors (FPR) are chemoattractant receptors on phagocytic cells like human neutrophils. Stimulation of FPR with N-formylmethionyl peptides induces a variety of responses of these cells including chemotaxis, superoxide production, release of hydrolytic enzymes and reorganization of cytoskeletal structures [36,37]. Most of these responses appear to be mediated through activation of phospholipase C, however, participation of other effector enz)nnes such as adenylyl cyclase, phospholipase D and phospholipase A2 have also been demonstrated [38]. 

The monoacetate [1152-14-3] M 252.2, m 223 is a fluorogenic substrate used for hydrolytic enzymes, and its fluorescence has Emax 593nm (Eex 500nm, in O.IM phosphate pH 8.0 with lipase) [Kitson Kitson Biochem J 322 701 1997]. [Beilstein 21IV 2263.]... 

At this juncture it is convenient to discuss the catalysis of ester hydrolysis by imidazole. The imidazolyl group of histidine is intimately involved in the mode of action of hydrolytic enzymes, and the two pathways believed to operate, general base catalysis and nucleophilic catalysis, were described in CHEC-I. In the latter, a 1-acetylimidazole is formed as an intermediate. General base catalysis has been proposed in the intramolecular thiolysis of A-propyl-2-thiomethylbenzamide... 

Lipids are hydrolysed for example, wax esters are converted into their constituent fatty acids and alcohols. The less soluble components tend to exhibit the greatest inhibition to ingress of hydrolytic enzymes, and so are the most stable towards biodegradation. The waxy components forming the cuticles of plant leaves and stems are among the best preserved biomacromolecules over geological periods (see Section 4.4.la).The transformations of lipids are examined in more detail in Chapter 5. 

A primary function of eosinophils is to destroy parasites such as worms. The eosinophilic granules are lysosomes containing hydrolytic enzymes and cationic proteins, which are toxic to parasitic worms. Eosinophils have also been implicated in asthma and allergic responses, although their exact role in the development of these disorders is still unknown, and this is an active area of research. 

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